Oil canning of mesh screen for filter

ABSTRACT

A method of reducing if not eliminating the possibility of tearing or ripping of a mesh screen of a filter during the manufacturing process includes the step of intentionally deforming the mesh screen. With this technique, as the plastic material that forms the frame of the filter begins to expand or change shape, as a result of the heating and squeezing steps involved with the molding process, the deformed mesh screen will be able to stretch or expand without the potential of tearing or ripping of the mesh screen. With the invention, numerous shapes and configurations of tools may be used to provide the intentional deformation of the mesh screen during the manufacturing process as well as to provide for control over the amount and degree of mesh screen deformation. Also, the resulting filter will have a mesh screen that has improved retention capabilities which will enhance the performance of the filter.

FIELD OF THE INVENTION

The present invention relates generally to the manufacture of filtersfor automotive applications and more specifically to deforming the meshscreen of the filter to allow for expansion of the filter frame and themesh screen during the manufacture of the filter.

BACKGROUND OF THE INVENTION

It is known that in automatic transmissions of vehicles, for example, atransmission filter is used on the inlet side of the transmissionhydraulic pump. The transmission filter, typically a fine mesh screen orsimilar filtering media, prevents harmful contaminants from entering thehydraulic system where they can increase wear and cause scoring andsticking of hydraulic control valves. If a major part fails inside thetransmission, the transmission filter may prevent pieces of that partfrom contributing to a more catastrophic transmission failure. Normally,transmission filters trap metal chips from parts such as gears andbushings and the normal fine material that results from wear of thehydraulic clutch facings and bands.

The known transmission filters are typically made of a plastic materialformed as a frame around a mesh screen—the plastic frame molded into thedesired configuration and onto the mesh screen. A rubber seal may beadded to or molded with the frame. The rubber seal is used to seal thefilter onto the inlet side of the hydraulic pump.

The known transmission filters, however, are currently manufacturedusing techniques that have certain drawbacks. For example, the moldedplastic frame that forms the perimeter or outer edge of the filter alsoforms individual, smaller sections or windows within the frame. The meshscreen extends across some or all of the smaller sections or windows,creating individual filter sections. Depending on the application, afilter may have one or more individual sections or windows within thefilter, with each section having a unique shape and configuration. As aresult, the filter must be molded to form each of these individualsections or windows. During the molding process, the plastic materialthat forms the frame of the filter is typically injection molded in thedesired configuration and molded at an elevated temperature over thescreen sections. At this elevated temperature, the plastic material thatforms the frame and individual sections may change shape andconsequently may stretch the mesh screen material that extends acrossthe individual section, sometimes to the point of tearing or ripping ofthe mesh screen material. In other applications, where a rubber seal isadded to the filter, a liquid injection molding process is used wherethe rubber seal is pressed or squeezed onto the filter frame at anelevated temperature. In these applications, the elevated temperatureand the pressing of the rubber seal causes the plastic material thatforms the frame to expand or change shape resulting in the stretching ofthe mesh screen, again sometimes to the point of tearing or ripping ofthe mesh screen.

The present invention is directed at overcoming the known problem oftearing or ripping of the mesh screen as well as other known drawbackswith respect to the manufacture of filters and more broadly theapplication of molded plastic onto a mesh screen material.

SUMMARY OF THE INVENTION

The present invention is directed to a technique for reducing, if noteliminating, the possibility of tearing or ripping of the mesh screen ofa filter during the manufacturing process. With the teachings of theinvention, the mesh screen is intentionally deformed to provide the meshscreen with an “oil canned” effect. With this configuration, as theplastic material that forms the frame of the filter begins to expand orchange shape, as a result of the heating and squeezing steps involvedwith the manufacturing process, the deformed mesh screen will also beable to stretch without the potential of tearing or ripping of the meshscreen. The invention contemplates numerous shapes and configurations oftools that will provide the desired “oil canned” effect or intentionaldeformation of the mesh screen during the manufacturing process. Theinvention provides for control over the amount and degree of mesh screendeformation, as well as improving the retention forces on the meshscreen which improves the performance of the filter. The invention maybe used with the manufacture of numerous types of filters and is alsoapplicable to the manufacture of any part that requires the molding of amesh screen material to a plastic material.

Other features and advantages of the invention will become apparent tothose skilled in the art upon review of the following detaileddescription, claims and drawings in which like numerals are used todesignate like features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an exemplary embodiment of a filtermanufactured according to the teachings of the present invention.

FIG. 2 is a partial cross-section view of a typical tool used to holdthe mesh screen during the manufacture of the filter.

FIG. 3 is a partial cross-section view of the filter made by the tool ofFIG. 2.

FIG. 4 is a partial cross-section view of a tool used to hold the meshscreen during the manufacture of the filter according to the presentinvention.

FIG. 5 is a partial cross-section view of the filter made by the tool ofFIG. 4.

FIG. 6 is a partial cross-section view of another tool used to hold themesh screen during the manufacture of the filter according to thepresent invention.

FIG. 7 is a partial cross-section view of the filter made by the tool ofFIG. 6.

Before the embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is to be understood that thephraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting. The use of“including” and “comprising” and variations thereof is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items and equivalents thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, an exemplary embodiment of a filter 10 madeaccording to the teachings and principles of the present invention isdepicted. The filter 10 is exemplary of a transmission filter and isexemplary of the numerous shapes and configurations of the possiblefilters that may be made according to the teachings of the invention.The filter 10 includes a filter frame 12 that forms or defines numerousframe sections 14. As illustrated, each section 14 may define numerouspossible shapes and configurations depending on the desired application.The frame 12 may be made of numerous materials, including a nylonmaterial, such as 33% glass filled nylon 6/6.

The frame 12 may include a track or channel 16 in which a silicone orrubber material may be added during a liquid injection molding process.The silicone or rubber material forms a seal around each of the sections14. As illustrated, the track 16 containing the silicone or rubbermaterial forms a continuous track that extends around each of thesections 14 and the silicone or rubber material prevents any leakingaround each of these sections. The frame 12 may also include one or moremounting holes 18 that serve to mount the filter 10 at the desiredlocation, such as to the inlet side of a transmission pump.

A mesh screen 20 is formed with the frame 12 using a plastic moldingprocess, as described below. The mesh screen 20 may be made of numerousmaterials, including a polyester or nylon material, as well as stainlesssteel, or other suitable material. The mesh screen 20 is configured toextend across the sections 14 and serves as a filtering media to filtercontaminants from a fluid or liquid, such as transmission fluid, as thefluid or liquid passes through the mesh screen 20.

Referring to FIG. 2, a cross-section of a known tool 30 that is used tohold the mesh screen in position during the plastic molding processincludes tool halves 32, 34 each having planar, opposing surfaces 36,38. As known, the surfaces 36, 38 hold the mesh screen during themolding process while the injected plastic material flows throughcavities 40, 42 to form the frame 12. The frame 12 and accompanying meshscreen 20 are then placed in a mold for the liquid injection moldingprocess during which the silicone or rubber material that forms the sealis added to the track 16, and the frame 12 is squeezed in the mold todefine the final configuration of the filter 10.

FIG. 3 shows a cross-section of the molded frame 12 with the mesh screen20 extending between the frame 12 as formed by the known tool 30 of FIG.2. As illustrated, the mesh screen 20 is planar or flat to match theshape of the opposing surfaces 36, 38, and is held in position by theframe 12. With the use of the type of tool 30 depicted in FIG. 2, as theplastic material that forms the frame 12 begins to expand or changeshape, as a result of the plastic material being heated to approximately300 degrees Fahrenheit during the liquid injection molding process andsqueezed, the mesh screen 20, because it is flat or planar, will have atendency to be stretched between the frame 12 sections, sometimes to thepoint of tearing or ripping of the mesh screen. More specifically and byway of example, if the frame material consists of a nylon materialhaving a coefficient of thermal expansion ranging from 1.0×10(−5)in./in./° F. to 5.0×10(−5) in./in./° F., when this material is exposedto a temperature of approximately 300 degrees Fahrenheit, the materialmay expand linearly approximately 0.0003 to 0.015 inches. This degree oflinear expansion may result in the tearing or ripping of the mesh screenthat is molded with the frame 12.

Referring to FIG. 4, a cross-section of a tool 50 that may be used withthe teachings of the invention is depicted and includes tool halves 52,54. The half 52 defines a recess surface 56, and the half 54 defines aboss surface 58. The recess surface 56 may define angled wall surfaces59 that join with a flat bottom wall surface 61. The boss surface 58 maydefine angled wall surfaces 63 that join with a flat top wall surface65. The recess surface 56 and boss surface 58 are mating in that thesurfaces 63 and 65 of the boss surface 58 will seat within the surfaces59 and 61 of the recess surface 56, as illustrated by FIG. 4. The recessand boss surfaces are used to hold the mesh screen 20 in position duringthe molding process. Importantly, the recess and boss surfaces alsointentionally deform the mesh screen 20 to form a dome shaped profile,as illustrated by FIG. 5, thus creating an “oil-canned” effect. Asdiscussed below, the “oil-canned” effect permits the mesh screen 20 tostretch or expand during the molding process, thereby reducing, if noteliminating the possibility of tearing or ripping of the mesh screen 20as the plastic frame material expands.

It should be understood that the recess surface 56 and boss surface 58may have other shapes and configurations, including spherical, angular,flat or curvilinear surfaces, or a combination of these surfaces, thatstill provide the desired “oil canned” effect or intentional deformationof the mesh screen. It is also contemplated that the tool 50 may be usedwith all the sections 14 (FIG. 1) to intentionally deform the meshscreen 20 within each of these sections.

Referring to FIG. 4, the tool 50 also defines cavities 60, 62 throughwhich flows the plastic material to form the frame 12 during the plasticmolding process. The frame 12 and accompanying mesh screen 20 is thenplaced in a mold for the liquid injection molding process during whichthe rubber or silicone material is added to the track 16 of the frame 12and then squeezed in the mold to define the final configuration of thefilter 10.

Referring to FIG. 5, there is shown a cross-section of the frame 12 withthe deformed mesh screen 20 extending between the frame 12. The meshscreen 20 is intentionally deformed at 70 by the tool 50 to provide themesh screen with a dome-shaped profile and thus the “oil canned” effect.With this configuration, as the plastic material that forms the frame 12and sections 14 begins to expand or change shape, as a result of theheating and squeezing of the plastic material as described above, thedome-shaped, deformed mesh screen 20, due to the additional mesh screenmaterial as well as its non-planar shape, will be able to stretch or beput in tension, thereby reducing if not eliminating the potential fortearing or ripping of the mesh screen. It should be understood that theinvention is not limited to the particular mesh screen deformationdepicted at 70, which shows a generally dome-shaped deformation. Rather,the invention contemplates any deformation of the mesh screen 20 thatstill permits the expansion of the mesh screen. Indeed, any non-planaror non-linear deformation of the mesh screen is contemplated with theinvention to achieve the benefits of the invention.

Referring to FIG. 6 there is depicted a cross-section of anotherexemplary tool that may be used with the teachings of the invention.Tool 71 includes tool halves 72, 74 that in use define a cavity 75formed by raised surface walls 76 and 77 and planar surface wall 81 ofthe tool half 72, and raised surface walls 78 and 79 and planar surfacewall 83 of the tool half 74. With this embodiment, the mesh screen 20 isdeformed or squeezed between opposing surface walls 77 and 78 and alsobetween opposing surface walls 76 and 79 during the molding process. Thesqueezing of the mesh screen is performed adjacent to the frame 12 andfor a distance of approximately 1 to 2 millimeters from the frame 12.The intentional deformation of the mesh screen 20 at this locationcauses the mesh screen to displace toward the center or middle of themesh screen to create the “oil-canned” effect, as illustrated by FIG. 7.Similar to the above embodiment, the “oil-canned” effect permits themesh screen 20 to stretch or expand during the molding process, therebyreducing, if not eliminating the possibility of tearing or ripping ofthe mesh screen 20 as the plastic frame material expands or changesshape.

Similar to the above embodiment, the tool 71 further defines cavities80, 82 through which flows the plastic material to form the frame 12during the plastic molding process. As described above, the frame 12 andaccompanying mesh screen 20 are then placed in a mold for the liquidinjection molding process during which the rubber material is added tothe track 16 of the frame 12 and squeezed in the mold to form the finalconfiguration of the filter 10.

Referring to FIG. 7, there is shown a cross-section of the frame 12 withthe deformed mesh screen 20 extending between the frame 12. With the useof the tool 71, the mesh screen 20 is intentionally deformed or squeezedat mesh portions 84 and 86 by the surface walls 76, 77, 78 and 79 of thetool halves 72, 74. As indicated above, the mesh screen 20 material willbe pushed or displaced toward a middle portion 88 that will have arelatively thicker cross-section then the portions 84 and 86. With thisconfiguration, as the plastic material that forms the frame 12 andsections 14 begins to expand or change shape, as a result of the heatingand squeezing of the plastic material as described above, the deformedmesh screen 20 will be able to stretch, thereby reducing if noteliminating the potential for tearing or ripping of the mesh screen.

With the principles and teachings of the invention, the amount anddegree of mesh screen deformation can be controlled. Also, the inventionprovides that the “oil canned” effect will be present, thereby reducingif not eliminating the likelihood of the mesh screen ripping or tearingwhen the plastic material that forms the frame expands or changes shape.In addition, the retention forces on the mesh screen of the finalconfiguration of the filter are improved, thereby permitting more fluidforce against the mesh screen during use of the filter without rippingor tearing of the mesh screen.

Variations and modifications of the foregoing are within the scope ofthe present invention. It should be understood that the inventiondisclosed and defined herein extends to all alternative combinations oftwo or more of the individual features mentioned or evident from thetext and/or drawings. All of these different combinations constitutevarious alternative aspects of the present invention. The embodimentsdescribed herein explain the best modes known for practicing theinvention and will enable others skilled in the art to utilize theinvention. The claims are to be construed to include alternativeembodiments to the extent permitted by the prior art.

Various features of the invention are set forth in the following claims.

1. A filter comprising: a frame defining frame sections; and a meshscreen molded within the frame sections, the mesh screen defining anon-planar profile to permit expansion of the mesh screen.
 2. The filterof claim 1 wherein the frame defines a plurality of frame sections withthe mesh screen molded with each of the plurality of frame sections. 3.The filter of claim 2 wherein the non-planar mesh screen is dome-shaped.4. The filter of claim 1 wherein the non-planar mesh screen includessqueezed portions.
 5. The filter of claim 1 wherein the frame defines atrack formed around the mesh screen.
 6. The filter of claim 5 whereinthe track includes a rubber material configured within the track.
 7. Amethod of manufacturing a filter comprising the steps of: molding aframe defining at least one frame section; molding a mesh screen acrossthe at least one frame section; and deforming the mesh screen; wherebythe deformed mesh screen permits expansion of the mesh screen.
 8. Themethod of claim 7 further comprising the step of molding a seal aroundthe at least one frame section.
 9. The method of claim 7 wherein the atleast one frame section is a plurality of frame sections.
 10. The methodof claim 9 further comprising the step of molding the mesh screen acrossthe plurality of frame sections.
 11. The method of claim 10 furthercomprising the step of deforming the mesh screen that extends across theplurality of frame sections.
 12. The method of claim 7 wherein thedeformed mesh screen has a non-planar profile.
 13. The method of claim12 wherein the non-planar mesh screen is dome-shaped.
 14. The method ofclaim 8 wherein the step of molding a seal around the at least one framesection includes the use of a liquid injection molding process.
 15. Amethod of manufacturing a filter comprising the steps of: molding aframe defining a plurality of frame sections; molding a mesh screenacross at least one of the plurality of frame sections; molding a sealaround at least one of the plurality of frame sections; and deformingthe mesh screen; whereby the deformed mesh screen permits expansion ofthe mesh screen.
 16. The method of claim 15 further comprising the stepof molding the mesh screen across the plurality of frame sections. 17.The method of claim 16 further comprising the step of deforming the meshscreen that extends across the plurality of frame sections.
 18. Themethod of claim 17 wherein the deformed mesh screen has a non-planarprofile.
 19. The method of claim 18 wherein the non-planar mesh screenis dome-shaped.
 20. The method of claim 18 wherein the non-planar meshscreen defines at least one squeezed portion and a non-squeezed portion.